Bimetallic sulfide FeNiS nanoparticles modified N/S co-doped carbon nanofibers as anode materials for high-performance sodium-ion batteries.

Transition metal sulfides (TMSs) have garnered significant attention owing to high theoretical capacities, favorable environmental compatibility, abundant natural resources, and suitable discharge/charge voltage platform in the field of anode materials for sodium-ion batteries (SIBs). However, the sluggish reaction rates and significant volume alteration during the process of sodiation/desodiation restrict the practical application of TMSs for SIBs. Herein, a novel bimetallic sulfide FeNiS nanoparticles modified nitrogen/sulfur co-doped carbon nanofibers (NSCFs) composite is successfully synthesized using a straightforward electrostatic spinning and sulfurization treatment. As an anode material for SIBs, FeNiS/NSCFs exhibits a high reversible specific capacity of 686.34 mAh g at 0.1 A/g and a capacity of 607.26 mAh g after 120 cycles at 1.0 A/g with a capacity retention rate of 96.9 %. Even at 10.0 A/g, it still maintains a capacity of 481.14 mAh g after 800 cycles, indicating an excellent electrochemical energy storage performance. Density functional theory calculations demonstrate that the FeNiS exhibits enhanced binding with NSCFs, promoted electron transfers, improved Na adsorption ability, and decreased Na diffusion barrier energy compared to those of monometallic sulfide FeS. Additionally, the three-dimensional network skeleton of NSCFs can effectively enhance the electrical conductivity and relieve the volume change during the discharge and charge process. The innovative multicomponent design and nanostructural configuration provide a promising strategy to develop high-performance anode materials based on bimetallic sulfide for SIBs.